Wildfire smoke and your HVAC: the Vancouver WA prep guide.

If you have lived through the 2020 Labor Day fires, the 2023 Canadian smoke season, or any August in the last five years, you know the routine: AQI numbers climb past 150, the sky goes orange, and homeowners suddenly remember they have an HVAC system. Most of the homes we walk through during a smoke event are doing the wrong things with it.

The good news: keeping indoor air clean during a smoke event is mostly about settings and filters, not about new equipment. Here is the protocol that actually works.

Step 1: Upgrade your filter to MERV 13.

The single most impactful change. MERV (Minimum Efficiency Reporting Value) is a 1–16 scale measuring how well a filter captures fine particles. Standard 1-inch furnace filters from the hardware store are usually MERV 8 — fine for dust, useless for wildfire smoke.

The EPA recommends MERV 13 as the minimum effective filter for wildfire smoke. MERV 13 captures roughly 95% of PM2.5 particles — the fine smoke particulates that do the actual damage to lungs and eyes.

Most residential furnaces can handle a MERV 13 filter in the same slot as a MERV 8. A few considerations:

• Airflow restriction. Higher-MERV filters are denser. If your system has marginal airflow already, jumping to MERV 13 in a 1-inch filter slot can starve the air handler. The fix is usually a 4-inch or 5-inch media cabinet, which has the surface area to handle MERV 13 without restriction.
• Sizing. Buy the exact size — filter dimensions are listed on the side of the existing filter. Off-by-half-an-inch filters let smoke bypass the media entirely.
• Brand. 3M Filtrete 2200, Honeywell Allergen Plus, and Aprilaire 213 (for media cabinets) all do well. Avoid no-name MERV 13 — the actual capture rates often do not match the label.

Step 2: Switch to recirculate mode.

Most Vancouver-area homes do not have an active fresh-air intake — but if yours does (some newer homes with HRV/ERV systems), shut it during smoke events. The whole point of recirc mode is to stop pulling outdoor smoke into the house and keep cycling the existing indoor air through your filter.

On a standard thermostat, this usually means setting the fan to "on" instead of "auto." That keeps air moving through the filter continuously, even when the system is not actively heating or cooling. Energy cost: roughly $5–$15/month in extra fan runtime. Worth it during smoke season.

Step 3: Replace the filter more often.

A MERV 13 filter that would normally last 90 days can clog in 30–45 days during heavy smoke. You can usually see it — the filter media goes from white to gray to dark gray. When airflow at supply registers feels noticeably weaker, replace it immediately.

We recommend keeping at least two spare MERV 13 filters in the closet during August and September. Cheap insurance.

Step 4: Add an air purifier (optional but real).

For homeowners who want another layer — especially anyone with asthma, COPD, young children, or elderly residents — we install whole-home air purifiers that integrate with the HVAC system. These are not the same as portable HEPA units.

The two we install most often:

• Aprilaire 5000 Electronic Air Cleaner. Sits in the return ductwork, uses electrostatic precipitation to capture particles down to 0.3 microns. Smoke is in this size range. Roughly $900–$1,400 installed.
• iWave-R Bipolar Ionization. Generates ions that bind to smoke particles, making them larger and easier for the filter to capture. Roughly $700–$1,100 installed.

Portable HEPA units (Coway, Levoit, Blueair, Austin Air) are excellent for bedrooms and the room where you spend the most time. We recommend one per bedroom for households with anyone in a sensitive group.

What does not help (and may hurt).

• Opening windows "for fresh air." Counterproductive during a smoke event. The outdoor air is the problem.
• Cracking a window at night when AQI drops. Tempting but usually a mistake. Smoke particulates settle but do not disappear, and you reintroduce them into the home.
• "Air cleaning" sprays or candles. Marketing. Some actively make air quality worse by adding VOCs.
• Running an attic fan or whole-house fan. These pull outdoor air directly into the home. Disable them entirely during smoke events.

What we install for clients who want a full solution.

The "set it and forget it" smoke-season setup we install most often:

1. 4-inch media cabinet retrofit on the air handler return (replaces the 1-inch filter slot)
2. Aprilaire 213 MERV 13 media filter (one filter, lasts 6–12 months in non-smoke conditions)
3. Smart thermostat with fan scheduling — set to circulate 20 minutes per hour by default, ramp to continuous during AQI events
4. Optional: Aprilaire 5000 or iWave-R for extra capture stage

Whole package runs $1,200–$2,400 depending on whether the media cabinet retrofit is needed and which purifier (if any) gets added. It is not a small investment, but it eliminates the August scramble for filters and the "is this MERV 13 actually working" anxiety.

The bottom line.

Smoke season is here to stay in the Pacific Northwest. The infrastructure to handle it is mostly already in your HVAC system — you just need the right filter and the right settings. MERV 13, recirc mode, frequent replacement, and a portable HEPA in the bedroom will get most households through any smoke event in good shape.

If you want help setting up the more involved solutions — media cabinet retrofits, whole-home purifiers — request a quote. We typically schedule these in May or June, before smoke season starts.